On Tue, Aug 01, 2017 at 05:06:51PM -0400, Chuck Lever wrote: > Since I converted NFSD to use the new rdma_rw API, I've been > struggling with how NFSD determines the size of its send CQ, and how > it provisions its send queue limit (ie, when it waits for more send > queue entries to become available). > > The problem arises because rdma_rw hides the exact number of send > WQEs it has provisioned. It determines this number based on the MR > registration mode (FRWR for iWARP devices, local DMA rkey for > others), but the mode itself is no longer exposed to ULPs. > > Thus when FRWR is in use, rdma_rw adds more WQEs, but NFSD is no > longer aware of this, does not provision a larger CQ, and does not > raise its send queue accounting limit. That means the extra WQEs are > never really used. > > At LSF this year, Christoph and Sagi proposed a simple API that > expose information about how many CQ entries are needed so that ULPs > can provision their CQs more accurately. Indeed clean API. Does it make sense to get rid of sc_max_requests and use this exported value directly? > > The first patch here is a pre-requisite for the third. The second > patch adds the new API. The third patch changes NFSD to use the new > API to provision its CQ and send queue accounting accurately. > > This approach was tested using the (fixed) force_mr core module > parameter. Good, I liked the word "tested" in the sentence :). > > > --- > > Chuck Lever (3): > svcrdma: Limit RQ depth > rdma core: Add rdma_rw_mr_payload() > svcrdma: Estimate Send Queue depth properly > > > drivers/infiniband/core/rw.c | 24 ++++++++++++++++++++ > include/rdma/rw.h | 2 ++ > net/sunrpc/xprtrdma/svc_rdma_transport.c | 36 +++++++++++++++++++++--------- > 3 files changed, 51 insertions(+), 11 deletions(-) > > -- > Chuck Lever > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html
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